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Abstract

Using adaptive optics imaging tools to image the living retina, numerous investigators have reported temporal fluctuation in the reflectivity of individual cone photoreceptors. In addition, there is cone-to-cone (spatial) variation in reflectivity. As it has only recently become possible to image the complete rod photoreceptor mosaic in the living human retina, we sought to characterize the reflectivity of individual rods and compare their behavior to that of foveal/parafoveal cones. Across two subjects, we were able to successfully track the reflectance behavior of 1,690 rods and 1,980 cones over 12 hours. Rod and cone photoreceptors showed similar regional and temporal variability in their reflectance profiles, suggesting the presence of a common governing physiological process. Within the rod and cone mosaics, there was no sign of spatial clumping of reflectance profile behavior; that is, the arrangement of cells of a given archetypal reflectance profile within the mosaic was indistinguishable from random. These data demonstrate the ability to track the behavior of rod reflectivity over time. Finally, as these and other reflectance changes may be an indicator of photoreceptor function, a future extension of this method will be to analyze this behavior in patients with rod photoreceptor dysfunction (e.g., retinitis pigmentosa, Usher’s syndrome, and congenital stationary night blindness).

Photoreceptor composite images for the foveal (0.5° temporal-superior) imaging locations. These images were created by aligning and averaging all 13 time points, and are shown using both a linear (left) and logarithmic (right) display.

Photoreceptor composite images for the peripheral (~10° temporal) imaging locations. These images were created by aligning and averaging all 13 time points, and are shown using both a linear (left) and logarithmic (right) display.

Movie sequence of hourly AOSO images of the cone mosaic in JC_0002, showing representative normalized cone reflectance profiles (Media 3). The archetypes shown are flat (top left), gradual (top right), oscillatory (bottom left), or abrupt (bottom right). The circles in the retinal image are color coded to their respective profile plot, and their size was chosen for improved visualization and does not represent the area over which reflectance was analyzed.

Movie sequence of hourly AOSO images of the rod mosaic in JC_0138 showing representative normalized rod reflectance profiles (Media 4). The primary archetypes were flat (top left), gradual (top right), oscillatory (bottom left), or abrupt (bottom right). The circles in the retinal image are color coded to their respective profile plot, and their size was chosen for improved visualization and does not represent the area over which reflectance was analyzed.

Histogram of normalized reflectance of the cone and rod photoreceptor mosaics, for the 11am time point. Both the rods and cones each show significant variation in reflectivity, and similar results were observed at the other time points. This figure corrected August 15, 2011.

Cumulative histogram comparison (CHC) plots for the linear reflectance profile cells. In each plot, the solid line represents the fraction of intercell separations within a given distance for the actual cone or rod mosaic versus that for the average of 1000 random simulations. The minimum and maximum bounds of these simulations is given as the dashed lines. The insets show areas of the CHC plots where the actual data approaches or exceeds the bounds of the random simulations.